1. Field of the Invention
The present invention relates to a patch antenna and a method of mounting the same.
2. Description of Related Art
A conventional patch antenna has a radiation electrode on the upper surface of a dielectric substrate provided with a vertical through-hole, and a ground electrode on the lower surface of the dielectric substrate. The upper end portion of a feed pin inserted into the through-hole is electrically connected with the radiation electrode by solder. The lower end portion of the feed pin is arranged inside a recess in the lower surface of the dielectric substrate, the recess having an inner periphery greater than the diameter of the through-hole. The lower end of the feed pin is substantially flush with the lower surface of the ground electrode. The patch antenna is thus ready to be surface-mounted (e.g., Japanese Unexamined Patent Application Publication No. 2005-260875).
In order to surface-mount the patch antenna disclosed in Japanese Unexamined Patent Application Publication No. 2005-260875 on a mounting board, the lower end of the feed pin of the patch antenna is put into contact with the feed pad of the mounting board. Alternatively, cream solder is applied on the feed pad of the mounting board in advance, and then the cream solder is melted by heat so that the melted solder climbs along the feed pin. This electrically connects the lower end portion of the feed pin of the patch antenna and the feed pad of the mounting board. In the latter method using the cream solder, the recess in the lower surface of the dielectric substrate ensures a space to firmly attach a conductive material, such as solder, to the feed pin and prevents the solder from coming into contact with a ground electrode.
With the patch antenna disclosed in Japanese Unexamined Patent Application Publication No. 2005-260875, the lower end of the feed pin is substantially flush with the lower surface of the ground electrode, as described above. In the former method, the feed pin cannot completely come into contact with the feed pad in some cases after the patch antenna is placed on the mounting board.
Specifically, in the case where the dielectric substrate and/or the ground electrode of the patch antenna are not flat or the feed pad on the upper surface of the mounting board is not flat, the lower end of the feed pin may fail to come into contact with the feed pad.
Due to the same reason, the lower end of the feed pin and the cream solder also cannot be appropriately in contact with each other in the latter method in some cases. Thus, the melted solder does not climb along the feed pin adequately, leading to failure to form a preferable solder fillet.
Slightly projecting the lower end portion of the feed pin from the lower surface of the ground electrode to prevent such circumstances may damage the feed pin since the projection of the feed pin comes into contact with some external object during transportation. Furthermore, projecting the lower end portion of the feed pin from the lower, surface of the ground electrode may damage the feed pad since the lower end of the feed pin strongly comes into contact with the feed pad before the other portions of the patch antenna come into contact therewith when the patch antenna is placed on the mounting board.
In addition, the patch antenna may be tilted at the pivoting contact point of the feed pin and the feed pad, thus leading to mounting of the patch antenna in the tilted state.